People who work long hours or overtime may face an increased risk of sickness and injury.

The risk exists regardless of job type, according to researchers of a new study, which appears in Occupational and Environmental Medicine.

Their conclusion supports growing evidence that long working hours negatively affect workers' health and well-being.

This study "adds to the growing body of evidence indicating that work schedules involving long hours or overtime substantially increase the risk for occupational injuries," writes researcher Allard Dembe of the Center for Health Policy and Research at the University of Massachusetts.

In the U.S., up to a third of overtime is compulsory, according to the researchers.

Those who routinely put in overtime or work a long day are thought to be at heightened risk for a variety of ailments, including high blood pressure, heart disease, depression, diabetes, chronic infections, general health complaints, and even death, write the researchers.

Researchers studied nearly 11,000 workers. They evaluated workers' job histories, work schedules, and occurrence of occupational injury and illness between 1987 and 2000.

In total, they analyzed more than 110,000 job records.

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During the 13-year study period, there were 5,139 work-related injuries and illnesses. More than half were in jobs with extended hours or overtime.

Employees who worked overtime were 61 percent more likely to sustain a work-related injury than those who did not work overtime.

Compared with those who worked fewer hours, they also found:

—Working at least 12 hours a day was associated with a 37 percent increased risk of injury or illness.

—Working at least 60 hours a week was associated with a 23 percent increased risk.

Although the risk of illness and injury increased depending on the number of hours worked, long commutes had no impact on the illness/injury rate, they write.

Nor were the risks based on employees working in jobs or industries that were inherently "riskier."

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SOURCES: Dembe, A. Occupational and Environmental Medicine, 2005; vol 62: pp 588-597. News release.